The present proposal has as its primary objective prevention of chemical carcinogen induced neoplasia of the large bowel. The proposed means of achieving this goal is by the use of antioxidants. Two types of antioxidants will be employed; a group which is not absorbed from the gastrointestinal tract and a second group which is absorbed from this site. Depending on the results obtained, further work will be carried out to determine the mechanism of any inhibition observed and the conditions under which it occurs.